Last spring frost
May 10
Frost Dates for Richland, OR
First fall frost
Oct 1
Growing season
141 days
Hardiness zone
6b
In an average year around Richland, OR, the last spring frost (32°F) is about May 10 and the first fall frost is about Oct 1, giving roughly a 141-day growing season. To be safe most years, wait until Apr 27 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Jun 16 | May 28 | May 9 |
| Freeze (32°F) | May 29 | May 10 | Apr 27 |
| Hard (28°F) | May 15 | Apr 28 | Apr 13 |
| Severe (24°F) | May 4 | Apr 13 | Mar 21 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 16 | Jun 8 | Jun 4 | Jun 1 | May 28 | May 23 | May 19 | May 15 | May 9 |
| 32°F | May 29 | May 21 | May 16 | May 13 | May 10 | May 7 | May 4 | Apr 30 | Apr 27 |
| 28°F | May 15 | May 8 | May 4 | Apr 30 | Apr 28 | Apr 25 | Apr 22 | Apr 19 | Apr 13 |
| 24°F | May 4 | Apr 27 | Apr 21 | Apr 17 | Apr 13 | Apr 10 | Apr 6 | Apr 1 | Mar 21 |
| 20°F | Apr 12 | Apr 5 | Apr 1 | Mar 28 | Mar 20 | Mar 13 | Mar 8 | Mar 3 | Feb 25 |
| 16°F | Mar 18 | Mar 9 | Mar 3 | Feb 27 | Feb 23 | Feb 18 | Feb 13 | Feb 5 | Jan 27 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Sep 4 | Sep 19 | Oct 2 |
| Freeze (32°F) | Sep 16 | Oct 1 | Oct 13 |
| Hard (28°F) | Sep 28 | Oct 11 | Oct 25 |
| Severe (24°F) | Oct 6 | Oct 22 | Nov 8 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 4 | Sep 10 | Sep 14 | Sep 17 | Sep 19 | Sep 21 | Sep 24 | Sep 27 | Oct 2 |
| 32°F | Sep 16 | Sep 21 | Sep 24 | Sep 28 | Oct 1 | Oct 3 | Oct 5 | Oct 9 | Oct 13 |
| 28°F | Sep 28 | Oct 1 | Oct 5 | Oct 8 | Oct 11 | Oct 13 | Oct 17 | Oct 20 | Oct 25 |
| 24°F | Oct 6 | Oct 11 | Oct 15 | Oct 19 | Oct 22 | Oct 25 | Oct 29 | Nov 2 | Nov 8 |
| 20°F | Oct 19 | Oct 25 | Oct 29 | Nov 1 | Nov 3 | Nov 7 | Nov 12 | Nov 17 | Nov 24 |
| 16°F | Oct 31 | Nov 5 | Nov 10 | Nov 16 | Nov 21 | Nov 25 | Nov 29 | Dec 5 | Dec 12 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Richland, Or, about 2 miles away@if(!empty($station['elevation_ft'])), at 2,215 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in Richland, OR?
On average, the last spring frost (32°F) around Richland, OR is about May 10. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 27.
When is the first frost in the fall?
The first fall frost around Richland, OR typically arrives about Oct 1. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around May 10 on average, or Apr 27 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 141 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 97870 Planting calendar → Oregon frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026